A vibration gyro element uses, as a vibration body, a piezoelectric monocrystal, such as quartz crystal, lithium niobate, or lithium tantalite, or a vibration plate to which a piezoelectric monocrystal is attached. Shapes of vibration bodies are various shapes such as a tuning fork shape, a square cross-sectional turning bar shape, an equilateral triangular cross-sectional turning bar shape, a circular cross-sectional turning bar shape, and an H shape (e.g., see Non-Patent Literatures 1 to 3 and Patent Literature 1).
Each of the vibration gyro elements described in Non-Patent Literatures 1 to 3 has one detection axis for detecting rotation. Thus, in order to detect rotation about a plurality of detection axes, a plurality of elements are needed. Meanwhile, the vibration gyro element described in Patent Literature 1 has a plurality of detection axes.
FIGS. 1(A) and 1(B) are diagrams illustrating a configuration example of a vibration gyro element obtained by referring to Patent Literature 1. FIG. 1(B) is a cross-section along line A-A′ in FIG. 1(A).
The vibration gyro element 101 includes a vibration plate 104, eight detection vibration bodies, and one drive vibration body. The drive vibration body includes a driving electrode 106, a piezoelectric substrate 107, and a driving electrode 108, and excites the vibration plate 104 to flexurally vibrate in a principal surface normal direction. Each detection vibration body includes a detecting electrode 102, a piezoelectric substrate 103, and a detecting electrode 105.
In the vibration gyro element 101, each detection vibration body is located so as to be symmetrical about each of two orthogonal detection axes (X1 axis, X2 axis). In a pair of detection vibration bodies located so as to face each other across a detection axis, in-phase alternating voltages are excited when a Coriolis force is not applied to the vibration plate 104, and the phase of an alternating voltage changes by an amount of change of reversed polarity when a Coriolis force is applied to the vibration plate 104. Thus, the difference between the alternating voltages excited in the pair of detection vibration bodies is obtained with a detection circuit, whereby it is possible to detect a Coriolis force generated by rotation about the detection axis sandwiched between these vibration bodies.
In a vibration gyro element having a plurality of detection axes, when a driving characteristic and a detection characteristic are similar for each detection axis, even if a detection circuit which detects rotation about each detection axis has the same circuit configuration, the detection circuit can detect rotation about each detection axis. The driving characteristic is a characteristic regarding the distribution of amplitude of flexural vibrations, and the detection characteristic is a characteristic regarding the distribution of amplitude of an excitation voltage.
Non Patent Literature 1: “Piezoelectric Vibratory Gyroscope,” The Journal of the Acoustical Society of Japan, vol. 45, No. 5, pp. 402-408, 1989.
Non Patent Literature 2: “Angular Rate Sensor of Piezoelectric Vibratory Gyroscope,” The Journal of the Institute of Electronics, Information and Communication Engineers, Vol. J78-C-I, No. 11, pp. 547-556, November 1995.
Non Patent Literature 3: “Electromechanical Devices Using LiNbO3 and LiTaO3 Piezoelectric Crystals” the Journal of the Institute of Electronics, Information and Communication Engineers, Vol. J87-C, No. 2, pp. 216-224, February 2004.
Patent Literature 1: Japanese Patent No. 3218702